Yeah, it's fast. You bought a good charger, and your battery wasn't empty (normally). Since the normal rate people recommend is 1C, that means it takes ONE hour (1 "c" = the mah rating of your battery, that's why 1.6 amp was suggested as a speed) to charge it fully, give or take a couple of minutes since the charger is not constant (going slower in the end to do a better charge).

Now, since you left it on auto, the charger, well, charged at the fastest rate it deems to be safe, which means that it takes 30 minutes for 2c, etc, etc.